freesewing/markdown/dev/guides/plugins/conditionally-loading-build-time-plugins/en.md

title	order
Conditionally loading build-time plugins	30

You can choose to load your build-time plugin conditionally based on run-time data.

To do so, you need to create a condition method that will determine whether the plugin will be loaded. This method receives the complete settings object and should return true if the plugin is to be loaded, and false if it should not be loaded.

const condition = settings => {
  if (settings) {
    // Remember, settings contains:
    // settings.options => The user's options
    // settings.measurements => The measurements
    return true  // Load the plugin
  }
  else return false // Do not load the plugin
}

You pass your plugin and condition method as a third parameter to the Design constructor with the plugin and condition keys respectively.

Let's look at a complete example to illustrate this:

import freesewing from '@freesewing/core'
import plugins from '@freesewing/plugin-bundle'
import myConditionalPlugin from '@freesewing/plugin-bust'

const myConditionalPluginCheck = (settings = false) =>
  settings &&
  settings.options &&
  settings.options.draftForHighBust &&
  settings.measurements.highBust
    ? true
    : false

const Pattern = new freesewing.Design(
  config, 
  plugins, 
  { 
    plugin: myConditionalPlugin, 
    condition: myConditionalPluginCheck
  }
)

Our condition method will return true only if the following conditions are met:

• A settings object is passed into the method
• settings.options is truthy
• settings.options.draftForHighBust is truthy
• settings.options.measurements.highBust is truthy

This is a real-world example from our Teagan pattern. A t-shirt pattern that can be drafted to the high bust (rather than the full chest circumference) if the user choses so.

But that feat is handled auto-magically by plugin-bust which is a build-time plugin. So whether to load this plugin or not hinges on the user settings, which is why we load this plugin conditionally.